windows.h和MFC [英] windows.h and MFC

问题描述

为什么我不能在afx（MFC）项目中包含windows.h？

Why can't I include windows.h in afx(MFC) projects?

推荐答案

afx.h 或 afxwin.h （后者包括前者）。 windows.h 的前两行是

Typically, MFC application code includes afx.h or afxwin.h (the latter includes former). First two lines of windows.h are

#ifndef _WINDOWS_
#define _WINDOWS_

这意味着 _WINDOWS _ 如果包括该报头，则定义。
Afx.h 包括 afxver_.h ，此标头包含 afxv_w32.h 其中包含以下代码：

which means that _WINDOWS_ becomes defined if this header is included. Afx.h includes afxver_.h and this header includes afxv_w32.h which contains following code:

#ifdef _WINDOWS_
    #error WINDOWS.H already included. MFC apps must not #include <windows.h>
#endif
...
#include <windows.h>

$ b <在MFC头之前，你会得到在编译时生成的错误，如你所见，如果你包括 afxwin.h ，你不需要包括 windows.h 自己 - 它已经被 afxv_w32.h 包含。

So, if you include windows.h before MFC headers, you'll get this error generated in compile time and, as you can see, if you include afxwin.h you don't need to include windows.h yourself - it will already be included by afxv_w32.h.

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